Since last fall, I’ve been increasingly interested in the science of health and fitness. In November, I completed a dieting project in which I lost 30 pounds in about 3 months. After dropping the weight and getting down to a healthy BMI, I began to focus on exercise–discovering HIIT workouts as a sustainable and efficient way of staying in shape. But, eventually, I started asking myself the one question that I had never thought to ask: “Why am I doing this?”

To what end should I focus on health? Am I trying to become more physically attractive? Am I training to compete in something? What’s so important to me that I’m trying to get it by losing weight and getting my body in shape? When I started asking myself these questions, one answer kept coming back: I want to live longer.

Up until recently, sheer curiosity has driven my improvement in health. But, without some other motivation, I know I’ll eventually lose interest. Now, I believe I’ve found that motivation in longevity. The reason I want to improve my lifestyle is because I want to live a healthy life for a longer period of time. That means, I want to do things to my body that are going to help it resist illness and retain energy going into my later years of life.

Quiet serendipitously, I stumbled across a book on longevity earlier this month. As I look back my on my life, I’m betting that Spring Chicken: Stay Young Forever (Or Die Trying) by Bill Gifford is going to be one of those paradigm-shifting books that has shaped my thinking and guided my behavior more than most. While Gifford discusses the pursuit of longevity from many different angles, one interesting idea really jumped out at me–and that is the subject of this post.

Fasting has been a staple of the world’s key religions for centuries, but only recently has the practice become known for its scientific merit. Don’t get me wrong–the research is still new and there’s still a lot to learn. But intermittent fasting is quickly gaining traction in the academic community as an effective way to live a healthy life for a longer period of time.

Shortly after I read Spring Chicken, I read a book called The Fast Diet, which was referenced in Gifford’s book. The book proposes a certain method of fasting and I used some of the information to build my own fasting plan. I am now finishing up my second week of Intermittent Fasting. Here’s what my plan looks like:

Monday: Eat nothing throughout the day. Eat up to 600 calories between 6pm and midnight.

Tuesday: No restrictions; eat whatever I want.

Wednesday: Eat nothing throughout the day. Eat up to 600 calories between 6pm and midnight.

Thursday: No restrictions; eat whatever I want.

Friday: Eat nothing throughout the day. Eat up to 600 calories between 6pm and midnight.

Saturday: No restrictions; eat whatever I want.

Sunday: No restrictions; eat whatever I want.

So, essentially, I’m fasting 3 days a week and eating without restriction the other 4. I drink water, coffee, and tea while I’m fasting but nothing else. I get hungry usually by mid afternoon, but it usually goes away in a couple of hours and–by dinner time–I’m really not that hungry. I eat a small amount in the evenings, and it helps the hunger pangs from disturbing my ability to sleep. On my non-fast days, I don’t count calories but–based on previous testing–I’m estimating I eat an average of ~2,700 calories. Averaged out for the week, that puts me at my target of 1,800 calories per day.

So, am I living longer? Obviously, that’s impossible to tell. I won’t be able to know if fasting has helped me live longer than average until I surpass the age of the average person who doesn’t fast. And, even then, there are a whole host of variables that play into how long I live–so it’s difficult to isolate fasting as a variable. But, alas, there are several other great reasons for fasting. And, as time goes on, I’ll actually be able to see whether or not these benefit me in my own personal fasting regime. So, let’s talk about my complete list of reasons for intermittent fasting:

Longevity. So, let’s start with my initial and still most important reason for fasting. Numerous studies have been conducted to support the possibility that the practice of fasting extends life. It has been shown to reduce the risk of cancer in mice and to extend the lives of several different species by reducing risk of diabetes, heart disease, and more. Human trials are still a little sparse, but one study found that 60 elderly people spent 219 days sick and 13 of them died versus 60 other elderly people who fasted and spent 123 days sick while only 6 died. Regardless, I have found exactly zero evidence that fasting has any harmful effects on longevity, so why not give it a shot?

Weight Management. What’s really happening when fasting increases longevity, in most cases, is that people are simply reducing their overall calorie intake. Thus, many researchers believe that it’s the caloric restriction–rather than the fasting–that really increases longevity. Nevertheless, if fasting only serves as an effective means to the end of reducing calorie intake, it’s worth it. If there is one thing that is clear from epidemiological research, it is that obesity severely increases risk of early death from its role in diabetes, heart disease, various cancers, and more.

Hormesis. Although the research is somewhat controversial and abstract on this idea, it is believed among some researchers that introducing small shocks to our bodies by fasting initiates repair mechanisms that increase metabolism, burn fat, and strengthen our cells. Or something. Researchers call this idea hormesis. I don’t really understand it that well, but it’s the basis behind tearing our muscles so that they can rebuild, allergy shots, and Nassim Taleb’s book Antifragile. What doesn’t kill you makes you stronger. In fasting, what doesn’t starve you makes you stronger.

Hedonic Adaptation Prevention. Although this doesn’t have to do specifically with fasting, there is a well-supported phenomenon in psychology in which we are able to quickly adapt to both painful and pleasurable experiences. Once we get used to something that makes us happy, it quickly loses its luster. In one study, people who did the same nice thing for others over and over again felt less good about it later on than those who were able to change the nice thing they were doing for others–and that’s just one handy example I had. How does this relate to fasting? When I eat whatever I want–day in and day out–even the most delicious food starts tasting bland. When I deprive myself for a while, I reintroduce novelty into eating and even the blandest foods taste great.

Increased Energy. Until I see some solid research on this, I’m chalking this up to speculation. But there’s an idea that fasting is the natural state–as handed down to us by our hunter-gatherer ancestors. Due to the scarcity of food, they ate in a feast-and-famine sort of way. So, biologically, we are equipped to do the same. According to this theory, we have the most energy when we are hungry because we needed it at some point in the past to hunt for our food. Again, I don’t know if this is true. But it could be. It’s hard to sleep on an empty stomach anyway, but I’m not really sure if that’s the same thing.

Variety in Diet. Other diets I’ve tried restrict certain kinds of food. No carbs. No fat. No this. No that. Not so with fasting. When I restrict my diet on some days, I can eat with abandon on others. I’ll have pizza. I’ll have ice cream. Because, you know what, life is too short not to (but hopefully longer with fasting). That being said, I’m still going to be smart about it. Sweets and fats I’m still going to treat as a luxury, but I will have them. Most non-fast days, I’ll be sticking to a Mediterranean diet, because that has some solid research for increasing longevity as well. But, on occasion, I’ll eat whatever my greedy heart desires.

Convenience. It’s easy. On non-fast days, I don’t have to count calories or watch what I’m eating. And, on fast days, I simply don’t eat. Easy peasy. I can still eat with friends, because I’m not fasting on weekends. Saving all my daily fast-day calories for the evening, I can also still eat a small dinner with my wife. I’ve found something that works for me, and I won’t even have to think about it–as long as I can remember what day of the week it is.

So, there you have it. Obviously, I may not continue doing this forever. Like everything else in my life, it’s a test. If I think it’s working, I’ll keep doing. If not, I’ll try something out. But the current research is awfully persuasive, and I kinda like my reasons. Who knows? I might just be an intermittent faster until the day I die.